VP | R Documentation |
Calculate actual vapour pressure [kPa] either from psychrometric data or from relative humidity data.
VP( Tmax = NULL, Tmin = NULL, Rhmax = NULL, Rhmin = NULL, interval = "day", Tmean = NULL, Rhmean = NULL, Twet = NULL, Tdry = NULL, apsy = NULL, P = NULL )
Tmax |
maximum temperature during 24-hour period (for daily values) |
Tmin |
minimum temperature during 24-hour period (for daily values) |
Rhmax |
maximum relative humidity [precent] (for daily values) |
Rhmin |
minimum relative humidity [precent] (for daily values) |
interval |
hour, day, week or month |
Tmean |
Mean air temperature [degreeC] (for periods shorter 1 day) |
Rhmean |
Mean air humidity [percent] (for periods shorter 1 day or if Rhmax and Rhmin are missing) |
Twet |
wet bulb temperature (for calculation with psychrometric data) |
Tdry |
dry bulb tamperature (for calculation with psychrometric data) |
apsy |
coefficient depending on the type of ventilation of the wet bulb [kPa/(degreeC)] (for calculation with psychrometric data) |
P |
atmospheric pressure [kPa] |
must be provided as.numeric (1-366) or as a common date-time object (e.g, POSIXct, POSIXlt or Date objects). All formats for which is.timepoint from the lubridate package returns TRUE can be used
- use hour for periods <= one hour
- for day, week or month the same equations are used
eq. 17 of reference (Determination of actual vapour pressure from relative maximum and minimum humidity)
eq. 15 of reference (Actual vapour pressure derived from psychrometric data) (see psyc_cons
)
eq. 19 of reference (used in the absence of RHmax and RHmin)
eq. 54 of reference (for periods shorter than a day)
Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. FAO, Rome, 300(9).
e0
, satVP
VP(Tmax = 25, Tmin = 18, Rhmax = 82, Rhmin = 54) VP(Tmax = 25, Tmin = 18, Rhmean = 68)
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